EL7516(2005) Ver la hoja de datos (PDF) - Intersil
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Fabricante
EL7516 Datasheet PDF : 12 Pages
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EL7516
where:
IL = MOSFET current limit
IL-AVG = average inductor current
∆IL = inductor ripple current
∆IL
=
-V----I--N-----×-----[--(---V----O-----+-----V-----D----I--O----D----E----)----–----V----I--N-----]
L × (VO + VDIODE ) × FS
VDIODE = Schottky diode forward voltage, typically, 0.6V
FS = switching frequency, 600KHz or 1.2MHz
IL-AVG
=
I--O-----U----T--
1–D
D = MOSFET turn-on ratio:
D = 1 – ------------------V----I--N--------------------
VOUT + VDIODE
The following table gives typical maximum Iout values for
1.2MHz switching frequency and 22µH inductor:
TABLE 1.
VIN (V)
2.5
VOUT (V)
5
IOMAX (mA)
570
2.5
9
325
2.5
12
250
3.3
5
750
3.3
9
435
3.3
12
330
5
9
650
5
12
490
Thermal Performance
The EL7516 uses a fused-lead package, which has a
reduced θJA of 100°C/W on a four-layer board and 115°C/W
on a two-layer board. Maximizing copper around the ground
pins will improve the thermal performance.
This device also has internal thermal shut-down set at
around 130°C to protect the component.
Layout Considerations
To achieve highest efficiency, best regulation and most
stable operation, a good printed circuit board layout is
essential. It is strongly recommended that the demoboard
layout to be followed as closely as possible. Use the
following general guidelines when laying out the print circuit
board:
1. Place C4 as close to the VDD pin as possible. C4 is the
supply bypass capacitor of the device.
2. Keep the C1 ground, GND pin and C2 ground as close as
possible.
3. Keep the two high current paths a) from C1 through L1, to
the LX pin and GND and b) from C1 through L1, D1, and
C2 as short as possible.
4. High current traces should be short and as wide as
possible.
5. Place feedback resistor close to the FB pin to avoid noise
pickup.
6. Place the compensation network close to the COMP pin.
The demo board is a good example of layout based on these
principles; it is available upon request.
11
FN7333.4
March 4, 2005
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